The attribute remap is capable of changing the name of an attribute, the value via a input/output min/max, or a ramp.  In practice this is great when you want an attribute renamed or existing within a different range of values.

Group/Group Type:

-  Allows the attribute remap to work only on a certain set of points or primitives.  For more information about groups, please visit the group node.

Class:

--  What kind of attribute are you trying to work on?  Is it a point attribute?  A Prim attribute?  That's what this setting means when it's asking you for the "class."

Original Name:

--  This is where you tell the attribute remap node which attribute you'd like to work on.

New Name:

--   If you'd like to rename the attribute, this is where you can do so.  Otherwise, just put in the same name that you used in the "Original Name" section.

Compute Range:

--  In order for this to work, make sure that you're trying to compute range on an integer or float attribute.  This will figure out the min/max value of the incoming attribute and fill in the min/max fields based on those values.  

Input Min/Max:

--  In most situations, you'll want to capture the min/max values of the incoming attribute.  If a value finds itself lower than the minimum or larger than the maximum, then it will just default to whatever you set in the "Out of Range" values parameter.

Output Min/Max:

--  Once you've captured the correct min/max range, what would you like the new range of values to be?  As an example, if the old min/max was anywhere between 0 and .1, you could specify a new range that's 0 and 200 with this Output Min/Max.  

Out of Range Values:

--  What happens if a value wasn't captured within the input min/max range?  This option answers that question.  Clamp to Edge value just says "use the output min/max value."  Linearly Extrapolate says "Guess what the value is going to be based on how fast the numbers were falling/rising in the range.  "Roll Cyclically" says to just repeat the distribution of min/max values any time it goes past the min/max.  As an example, if a value went past the max range, then it would start over again at the min.  If a value is under the min range, it would exist at the top of the range.

Use Ramp:

--  Ramps are useful for controlling the in-between values.  For more information about ramps, I would highly suggest visiting Houdini For the New Artist II.