What is the difference between prefixes об and по. For example облизать and полизать.
Roughly said, об- means '[centered] around' and по- means 'along [and then to somewhere else]'. The difference is also in cases for adverbial complement - not always but quite often, e. g.
Дети облазили чердак. = The kids have investigated all the loft through.
Я обдумаю это. = I'll think about this.
Она обделала порог. = She shat around [all] the threshold.
Дети полазали на чердаке. = The kids has been investigating the loft [for a while].
Я подумаю об этом. = I'll think about this [and then I'll shift to some other topic].
Он поделал порог. = He's been making a threshold [for a while and then he switched to some other activity].
Sometimes the difference is that об- refers to a non-literal meaning, while по- indicates the action as it is, thus making the meaning entirely different, e. g.
Я обрёл смысл. = I've found [the supreme] meaning [of/in smth]. NB: the об- is regarded by some researchers as a part of the stem, but the stem actually is a historical cognate of Lithuanian ràsti and surė̃sti (acc. to Fasmer).
Я побрёл своим путём. = I wended my way along.
Дым обволок кострище. = The smoke coated the fireplace.
Волк поволок ягнёнка в тёмный лес. = A wolf was taking a lamb into a dark forest.
Дела обстоят хорошо. = The things / the circumstances are OK.
Они постоят и пойдут. = They'll stand there for a while and then they'll part.
Hence, the difference between облизать and полизать will be as follows:
Котёнок облизал сметану. = The kitten has licked [all the] sour creme [around].
Котёнок полизал сметану. = The kitten has licked some sour creme [for a while and then switched to some other activity].