Move the 5th to the bottom (D/A, for example) and we have a second inversion. If we were to take a dominant 7th chord and move the 7th to the bottom (D/C, for example), we’d have a third inversion.

and dominant 7th (eg E7). Let's look at the options when creating these 7th chords from a C root note. For Cmaj7 the notes would be - C (root), E (3rd), G (5th) and B (7th). For Cm7 the notes are ...