Road Wheels are a standard 27” better known as 700c. As the size is universal, the difference in road wheels is the depth of the rim, whether the rim is for tubular (no tubes) or clincher tyres (normal tyres and tube combination) and number of spokes used. Standard wheels have a traditional square profile alloy rim with 32 or 36 spokes and in this configuration the more you spend the lighter the wheel gets. Rims are available in clincher (normal tyre with separate tube) or tubular (one piece tyre and tube) versions which can only be used with corresponding types of tyres.
In the last few years the depth of the rim has increased and the number of spokes used dropped with these types of wheel referred to as deep section. Usually the more you spend the lighter the wheel but if you go for an aero deep section rim then be aware that they can weigh more than a standard wheel, the benefit being they are faster thanks to their aerodynamic properties.
Incidentally, road wheels will not fit mountain bikes so don’t buy a light set of road wheels thinking they will make your mountain bike lighter.