how do i populate a field in one shape file with data from another?

[MikeHenson]

heres the scenario....I am working with 2 shape files.  1 contains sewer lines. Just simple point 2 point lines.  The other shape file is "decade". It is a polygons of different decades that the sewer lines were built.  I would like to add a "decade" field to the sewer line shape file, based on which decade polygon is cover it. Does this make sense, and can anyone help me out on work flow? I'll attach an image. Thanks.  Notice in the image the liness are covered by the 1970 polygon. I'd like to add "1970" to a field in the sewer line file. Thanks for any help you can give.

[PeteCrosier]

Sounds like you're after a spatial join?

ArcGIS Help (10.2, 10.2.1, and 10.2.2)

Target - your lines

Join features - your polygons

Field map - the fields you want to include in the output line features

Match option / join operation - dependent on what you want to do with lines going across polygons / etc