They essentially share the same meaning.
However, there are differences.
grip: hold tightly, eg "a drowning swimmer now safely in the grip of a lifeguard" -- He could drown again, if he had not gripped the lifeguard.
grasp: apart from the meaning of "grip", it also means learning something intellectually. eg, Sonneblume graps some grammatical rules of English.
sieze: We usually say "sieze some opportunities".
Turn to an English-English dictionary for help, and you could find it easier to learn the differences between words.
BTW, could any natives help if 'among' is correct in the sentence 'What's the different among "grip","grasp","seize","grap".'?