Both of these have the same meaning, and different meanings. You can use however and though to mean "yet", "neverthless", "on the other hand" or "in spite of that". "However" can also mean "how", or "how, considering the circumstances". "Though" can also mean "like" when used with "as". "As though" means "similar to" or "as if".

Let's see how it works in practice: I understand you have doubts, however it's really important to ask. Though you have English classes, the practice is an important piece which will complete your learning.