Here's a breakdown:
* Se: This is a reflexive pronoun, indicating that the action of kissing is being done to themselves.
* estan: This is the present progressive form of the verb "estar" (to be), indicating that the action is happening right now.
* besando: This is the gerund form of the verb "besar" (to kiss).
Putting it all together, "se estan besando" translates directly to "They are kissing themselves." However, in English, we don't usually say "kissing themselves" when referring to two people kissing. So, the most natural translation is "They are kissing."