Road bike tyres should be chosen based on the tyre's diameter (it is important to choose exactly the same dimensions as your old tyre [650 or 700 mm]), the section, and the type of tread.
1. Tyre Section
The tyre's section is its width.
IF YOU ARE LOOKING FOR PERFORMANCE AND RESPONSIVENESS Go for a narrower section such as 23 mm.
The best compromise is a 25 mm section which is both comfortable and effective.
IF YOU ARE LOOKING FOR COMFORT Choose a tyre with a wide section such as 28 mm.
2. Tyre Tread Type
Flex or stiff bead?
STIFF BEAD A stiff bead tyre will be heavier but easier to assemble and more robust.
FLEX BEAD This type of tread is lighter and easier to transport (you can fold the tyre).