The general rule says that Present Continuous indicates an action that is taking place at the moment of speech. For example, when we say: Stasie is dancing with Homer, it means that the doer of the action is performing the action at the very moment of speech. It also implies that the action is in progress, i.e. it has started in the past, is happening at the moment and will end in the future. Another example: Kate is talking to her friend.
Present continuous is formed with the help of the auxiliary ‘to be’ in present simple and the verb in the ‘ing’ form: BE+Ving.
Apart from being used to indicate actions happening now, it also is used to indicate:
temporary activities: My cousin is staying with us until he finds somewhere to live.
situation of change: It is getting colder.
future arrangements (planned by the doer of the action): We’re throwing a party next Sunday.