The most obvious or direct use of auch is to mean also. Ich möchte auch Gitarre lernen. Auch ich möchte Gitarre lernen. I would like to learn Guitar. Someone can already or is learning now to play the Guitar. The speaker could also be expressing a desire to learn to play the guitar. I also would like to learn to play the Guitar. This may be used to emphasize that I also would like to play the guitar.
Occasionally, it is also possible to start a sentence with auch in German, but in such cases, auch does not have the meaning of also but instead often has the meaning of even though, or even. Auch wenn es möglich ist, sollen wir das nicht machen. Auch wenn es stürmig ist, fahre ich los. Even if it is possible, we shouldnt do that. Even if it is stormy, Im leaving.
Dont get the German words,,auch and,,also confused. By itself, auch means also in most cases whereas also has the meaning of therefore, then or thus in most cases. Es regnet heute. Also wir bleiben zu Hause. Sie ist krank. Sie wird also nicht kommen können. Its raining today. Therefore, we are staying at home. She is sick. She will thus not be able to come.