[dba-SQLServer] Covering Indexes

I need to understand covering indexes.  One of my databases has fields such
as 

PresenceOfChildren_00_02
PresenceOfChildren_03_05
PresenceOfChildren_06_10

Etc.  Thus what I need to know is do I need an individual index on each
field?  I get requests for data using selection criteria on just one, and
also sometimes on more than one of these fields.  If I have an index on all
of these fields together, will that help a query with selection criteria for
a single one of these fields?  On 3 out of 7 of these fields etc?

John W. Colby
Colby Consulting
www.ColbyConsulting.com