The 'sidewall' is the side of the tyre that we can see from looking at the side of the car. The markings on the sidewall tell us about the size, branding and construction of the tyre. For average drivers, most of this information is pretty meaningless but the basic tyre sizes - width, diameter and radius are important because it's these that we need to order the correct replacement tyres for your car.
The illustration below provides an explanation of the markings currently found on a tyre sidewall:

Contact details
COMPANY:
TyreQuote Ltd
TELEPHONE:
0800 019 3226
EMAIL:
help@tyrequote.com
POST:
TyreQuote Ltd
24 Rectory Road,
West Bridgford,
Nottingham NG2 6GB
OFFICE:
By appointment only