A primary verb is one of a group of three verbs that are important in English in the construction of aspect (progressive/continuous, perfect), voice (passive), and of negative, interrogative and emphatic forms of full verbs. The primary verbs are also among the most commonly used full verbs. The three primary verbs are be, have and do.
See main article Be.
As an auxiliary verb, it is used in the construction of the progressive/continuous aspect (progressive auxiliary) - My daughter is/was living in Manchester - and of the passive voice (passive auxiliary) - Luke was promoted last week.
See main article Have.
Have: (have, has, had, having) is used as a full verb with a variety of meanings, many associated with the idea of possession (Luke has a fantastic library) or experiencing/doing (I have a lot of problems with that. Mary has a shower as soon as she gets home from work.) It is also used causatively (I had the car serviced).
As an auxiliary verb, it is used in the construction of the perfect aspect (Have you finished yet? I wish you hadn't done that)
See main article Do.
Do: (do, does, did, done, doing) is used as a full verb with a variety of meanings (I must do something about that. Have you done your homework?).
As an auxiliary verb, it is used for three forms of the full verb: the negative (She doesn't like you), the interrogative (Did Paul say anything to you?) and the emphatic (We did enjoy the play). It is also used as code, standing in for the full verb in, for example, question tags (That went off quite well, didn't it?).