The topic shows that the proposition is only for that particular thing or aspect, and it implies that the proposition is not true for some others. For example, in "Az almát János látja". ('It is John who sees the apple'. Literally 'The apple John sees.'), the apple is in the topic, implying that other objects may be seen by not him but other people (the pear may be seen by Peter). The topic part may be empty.
the topic shows that the proposition is only for that particular thing or aspect and it implies that the proposition is not true for some others for example in "az almát jános látja" ('it is john who sees the apple' literally 'the apple john sees') the apple is in the topic implying that other objects may be seen by not him but other people (the pear may be seen by peter) the topic part may be empty