Antibodies are large proteins of the immune system that neutralize intruders, such as bacteria, viruses, fungi, and parasites. There are five main types of antibodies: IgA, IgD, IgE, IgG, and IgM.
To assist you in understanding IgG, IgM and IgA, I found some good articles and videos which do much better job explaining the differences than I can. I hope you find them beneficial.

IgM = Immunoglobulin M antibodies.
https://labs.selfdecode.com/blog/immunoglobulin-m/

Waldenstrom Macroglobulinemia cells make large amounts of a certain type of antibody (immunoglobulin M, or IgM), which is known as a macroglobulin. Each antibody (protein) made by the WM cells is the same, so it is called a monoclonal protein, or just an M protein.
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This video shows the differences between IgG and IgA serology tests and what the results can mean.
https://youtu.be/2eRpntScCmI

Though slow and as exciting as watching paint dry, this video lists each of the Antibodies, their structures and functions.
https://youtu.be/VctTbhhw8do
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In reference to the Kappa and Lamba light chains, they are primarily used in the typing of myeloma patients and determining the degree of disease in MM, B-cell Lymphomas and W/M patients.
This article helps give an understanding of a light chain and how the information is used in diagnosing blood disorders.

There are several National Institute of Health articles on using light chain in determination of B-cell lymphoproliferative disorders.

I know you have WM and B Cell lymphoma. How have you been doing since your Rituximab infusions? Have your symptoms progressed?