What is paired t-test, and under which circumstances should I use paired t-test? Is there any difference between paired t-test and pairwise t-test?
Roughly, paired t-test is a t-test in which each subject is compared with itself or, in other words, determines whether they differ from each other in a significant way under the assumptions that the paired differences are independent and identically normally distributed.
Pairwise t-test, on the other hand is a function in R which performs all possible pairwise comparisons. See this discussion for more information