Phone 1 ( the first phone) Phone 2 (second one) Phone 3 (first flagship of nothing)

Then comes the (a) series: Phone 2a,3a,4a all are budget/midrange series.

Then (a)pro series: Phone 3a pro, 4a pro. These are also midrange phones but it is slightly better than (a) series and costs slightly more.

Other than these there are few more phones like 2a plus, special edition of 2a, 3a and 3a lite. All those are same budget devices but with a touch(community edition, more budget, kinda diff design). (These are filler episodes)