Output Difinitions in Affymetrix Array @

Signal : 

A measure of the abundance of a transcript.

Detection : The call in an single-array analysis that indicates if the transcript was Present (P), Absent (A), Marginal (M), or No call (NC).
Detection p-value : p-value that indicates the significance level of the Detection call.

Change : The call that indicates the change in transcript level between a baseline and an experiment array.

Change p-value : p-value that indicates the significance level of the Change call.

Signal Log Ratio : The change in expression level for a transcript between a baseline and an experiment array. This change is expressed as the log2 ratio.