Granted Patents vs. Patent Application

Summarized from Patentlens.com:

At this point, the United States identifies granted (issued) patents with a seven-digit number followed by a B1 (patent not previously published) or a B2 (patent previously published), e.g., US 6,174,724 B1, The 'B1' and 'B2' are referred to as 'kind codes'.

Published U.S. Patent Applications are indicated with the year as a four-digit number and a publication number followed by an A1 (for the first publication), A2 (for republication) or A9 (corrected publication), e.g. US 2001/0002490 A1. This number is also referred to as the publication number on the USPTO PAIR (Patent Application Information Retrieval) web site.

In addition, there is also an application number In the U.S.  that is different than the publication number. This number is used to identify the case while it is pending with the USPTO. Application numbers consist of a two-digit 'series' number (usually 09, 10, or 11) that is separated from a six-digit number by a slash, e.g. 10/676,431.

Issued Patents in Europe are indicated with a seven-digit number followed by a B1, e.g. EP 0 458 846 B1. A 'B2' number indicates that the claims have been modified after grant.

Published European Patent Applications use the same numbering system but the number is followed by A1, A2, etc., e.g. EP 0 955 371 A1.