They are an easy identification of the tread type during the manufacturing and assembly process.
If you mean tire tread depth, the minimum is 1.6mm.
Tread wear indicator
As a verb, tread means the way someone is walking. As a noun, tread can mean the top of a stair (where you step on), or the tread of a tire.
Stripes on the tires are just identification used by the manufacturer. Different variations in stripe width, color, and count means a certain tread goes with a certain tire.
Tread wear indicator
It sounds like the tread width in millimetres
It is an indicator of tire tread wear.
That means it is a passenger car tire with tread width of 195 millimetres
It means it is a tire for a passenger car and tread is 235mm wide.
Minimum LEGAL tire tread depth is 2/32nds of an inch.
Tire spec in PA is 2/32 of an inch of minimum tread