How to read Map-Report in FPGA Synthesis Tools
These are defined in details in the document:

LatticeXP2 Family Data Sheet

If you go down to "Table 2-1. Resources and Modes Available per Slice" you will find the detailed description of how these slices are used and what kind of terminology they use when reporting the usage of them.

Let me know if this is OK, or I add more data to the answer to clarify it further