"езжать" is used: 1. as imperative. Imperative of "ехать" is highly unstable in Russian. ?Едь sounds strange and is rare. I disagree with Elena - may be for a modern Russian it sounds acceptable and even old-fashioned, but if you check in books - it is the rarest option! I think, in times of classic Russian literature it was, conversely 'folkish', not 'bookish'. ?Ехай can be met in dialects. Also in children speech. Sounds highly... dialectal/colloquial. Its users are likely to be laughed upon by snobs. езжай - is a comporimise form. It still sounds somewhat colloquial. поезжай - more common and somewhat more literary. Often, to avoid "colloquial" shades we just don't use imperative and say it diffrently, like "I advise you to go..." 2. in imperfective of prefixied forms: поехать - ?поезжать (rare unless as an imperative) проехать - проезжать наехать - наезжать выехать - выезжать объехать - объезжать 3. there is an additional (to those mentioned in your textbook:-)) verbal tense in Russian:) "езжать", also "езживать" can be used similarly to "бывать". I hesitate to define its semantics, because in modern Russian this form is getting less common (though бывать is common). May be in past it was just used for an action repeated many times. I'm not sure what they had in minds in 19 century:( In modern Russian it is stylistically marked, sometimes as a play. An educated Standard (!!!) Russian speaker would use it semi-jokingly, to imitate 'folkish' and archaic style.... ... OR, if he loves to read books (these forms are common in classic literatrue) - just to use the full richness of language, without jokes. Mostly it is used to mean: you had a habit of doing this in past, it was common and customary to do this. Он часто езжал к ним. Also to emphasize that you have experience of doing this (and more than once likely). Бывал я в Стамбуле. Видал я и не такое. Я такого отродясь не видывал!

"езжать" is usually used in imperative: "езжайте и посмотрите, что там происходит". You can also use "ездить" in this context: "едьте/съездите и посмотрите, что там происходит". But the 1st one is a more bookish option, perhaps old-fashioned to some extent.

I'd go crazy with so much grammar! Especially Russian grammar) Ok) Ездить means to go somewhere repeatedly, Езжай (a little better, perhaps, would be to say ПОезжай) is only used in Imperative form! You can also say съезди. The difference, as I feel it, is in the following: Езжай/поезжай домой, сегодня здесь нечего делать. Езжай/поезжай ко мне в отель и привези мне сменную одежду. But it is a bit better to say: Съезди ко мне в отель и привези мне сменную одежду. What I feel is this. Езжай/поезжай. Go somewhere. If nothing else is added it means just "go". Съезди implies going and coming back. In all the variety of Russian verbs what you need to grasp, to come to know is the meanings of prefixes. It will come. Be exposed to the language, it is the best way to understand it. It is easier and much more interesting than one can imagine) I wish you well.

I mix up these verbs of motion with each other, for there are too many of them :) Thanks

The verb "езжать" (if you mean it as an infinitive form) doesn't exist in Russian. You've probably mixed it up with another verb. There are a lot of verbs with the same root but with different prefixes, which give different meanings: приезжать, уезжать, отъезжать, выезжать, подъезжать etc.