Notwithstanding Harry's explanation of the nuances [small subtle differences] implied by these alternative forms, in practice they are used more or less interchangeably. (3) ie the use of the present continuous to refer to the future is slightly more casual and is mainly used in speaking. (1) is more likely than the others to be used in a written statement or agenda.

Hi Feifei Lu, Here is a detailed breakdown: My friends will come over to my house. This is a straightforward statement about a future event, indicating that your friends will visit your house at some point. My friends will be coming over to my house. This also indicates a future visit but suggests an ongoing action or a sense of anticipation, implying that the visit is part of a larger plan or process. My friends are coming over to my house. This indicates a future event using the present continuous tense, giving a sense of immediacy and certainty, as if the visit is imminent or definitely planned.

None has a single precise meaning. All vary according to context, where "context" means not just words spoken but the situation in which the words are spoken. #1 will usually be interpreted as (1a) a straightforward statement about what will happen in the future. It can also mean (1b) my friends habitually come over to my house. #2 will usually be interpreted as (1a). It can also mean (1b), that they are already repeatedly coming over to my house, or (2a) my friends will be repeatedly coming over to my house in the future. #3 is Present Tense. Beware! Present tense has myriad uses. The correct meaning should be clear from context. Possible meanings are (a) My friends are at this moment on their way to my house. (1a) is possible. (1b) is possible. (2a) is possible. Wow! #3 can mean ANY of the above possibilities. You can greatly limit the possible meanings through careful use of expressions like "tonight", "tomorrow", or "at this moment" to specify a time frame. That, not tense, is the true way that English conveys information about time. The word "will" gives less information about time frame than most learners realize. The true purpose of the word "will" in the English language is to express certainty or willfulness. Its connection to the future is that certainty facilitates statements about the future. The reason that #3 has such a vast array of interpretations is grammatical. From a grammatical perspective, all the sentence really does is to ascribe the adjective phrase "coming over to my house" to "my friends". That adjective phrase is timeless and means WHATEVER the speaker wants it to mean.