jajo - is a scientific and generic term for an egg
jajko is the colloquial word for typical eggs and also for testicles (though testicles are rather caller plural jaja or jajka)
jaje is an archaic form of the word 'jajo' only encountered in not very recent literary works especially poems
praca - a generic and formal word for 'work', also in the sense of 'workpiece'
robota - is a colloquial form but it has a notion of something that is at least slightly unwished for
światło is light
światłość is lightness (światłość is very much limited to spiritual or religious termniology)
more or less
zdjęcie is your generic and formal term for a 'photograph' but it has even more generic meaning that typical photography
fotka is a very colloquial name for photograph and it is simply short of 'fotografia' - 'fotographia' is mostly limited to typical photography (and not X-rays for example unlike zdjęcie) fotografia appart from being a name for a photograph is sometimes also used as a name for 'photography'
as książka is a diminutive form of księga the latter is something rather big, księga is also the word used for title of stories like in 'Księga dżungli' 'The Jungle Book' (R. Kipling) or 'Księga przysłów polskich' (The book of Polish proverbs) - also księga is sometimes used as a subdivision of a novel sometimes replacing chapters sometimes containing chapters
książka is a generic term
btw in other Slavic languages the unsuffixed word 'kniga, kniha' remained the generic word for book so the Czech 'knizka' is something smallish
królik - a rabbit
zając - a hare
truś/trusia is a sort of a pet name for rabbits (for hares less often because hares are rarely seen or kept as pets or a farm animal)
especially truś is used to call rabbits by farm housewifes for them to be fed
trusia is also part of a phrase 'siedzieć (cicho) jak trusia' remain silent and not to move - it is in relation to hares behaviour - they can remain sitting until mere meters from a person approaching or sometimes they can literally start before your very feet (not in the open though - in some vegetation even high grass)
biuro is generic (also formal) for an office - but in the physical sense rather - the office as a function or an institution is 'urząd' in Polish
gabinet has a notion of an office room that is used by a single person (some important person in an institution or a person who works for himself/herself like a writer, free lance researcher etc) while in a 'biuro' lots of people can actually work at the same time
gabinet is also the term used for a room where a doctor sees or treats his patiens - as an extrapolation gabinet is also used in more abstract sense as place where doctor sees his patients or even as a business entity of medical type (but rather a small one)
however biuro can also have a meaning of a company that is restricted to an office site - 'biuro matrymonialne', 'biuro projektowe'
this rather a grammar issue
jeść><zjeść the former is imperfective the latter perfective (simple non prefixed forms are typically imperfective but it's not an iron rule and there are imperfective verbs that have your typical prefixes (the prefixes are usually prepositions sometimes altered a bit)
if you haven't been taught what imperfective and perfective are then perfective is used when an action has been finished, completed, or just ended or is supposed to be finished in the future - as such perfective is never a thing of the now - so no perfective forms in the present tense
as you probably guess imperfective is simply more generic thing without determining if the action or the process have been completed - all verbs in the present tense are imperfective - if you want to say that some to actions or process is going to happen (or happened) simultanously with another the one (the longer) that you relate to is going to be in imperfective (Marek zadzwonił jak jedliśmy
z mamą obiad. Marek phoned when/as we were dining
sometimes differences are nuancical though
jadłem obiad - I was having a dinner zjadłem obiad - I had a dinner (but it's not that clearcut in actual use and you can often hear 'Jadłeś (już) obiad?' in a sense of 'Have you (already) had your dinner'
now a the issue of the so called frequentative
frequentative is a form of a verb that is used to show something happens in a repeated manner, typically, numerous times, from time to time - it can be very roughly explained as a difference between the English present simple and present continuous (very roughly because it is not always the case) - there are more or less strict rules how frequentatives are created in Polish (you have to take into account phonetical laws and irregularities of major verbs that spring from frequent use)
jem - I am eating jadam - I eat
jem śniadanie - I am having a breakfast śniadania jadam o szóstej - I have breakfast at six
(the thing is 'jem' can be often used instead of 'jadam' and definitely in this case - however 'jadam' cannot be used to mean 'i am eating')
the frequentative can be created (typically) equally from a perfective or imperfective verb (verb form) - so you've got 'jeść - jadać' but also 'zjeść- zjadać'
the thing is a frequentative of a given form is always imperfective (however a further perfective can be created of that imperfective frequentative with a prefix (pozjadać)) - so zjadać is imperfective an can be used in the present tense
Właśnie zjadam ślimaka - I am eating a snail right now (rather than I am having a snail right now) - but again 'jem' can be used here instead of 'zjadam' (as a form with a more general meaning)