The 12 digit National Grid Reference contains 10 numbers.

Q1: Am I right in thinking that the first 5 relate to easterly measurement, and the second five to northerly measurement?

Q2: What do each of these numbers mean, in metres/kmetres etc.? What I need to know us what is the size of the unit represented by the 1st digit of the set of five; the 2nd; 3rd; etc.

Grateful for early reply.

Thanks.