All these greek and latin terms are confusing. In good old english, what is lipoma?

Fatty tumor. Lipomas are benign (non-cancerous) fatty growths. They have been reported just about everywhere in the body, but are usually seen under the skin. They can be observed if they are small, but are commonly removed if they are enlarging, causing deformity, tender, etc. Generally, once removed, they do not return.
Lipoma is a fat lump. "lipo" in latin has to do with fat- so if you see a word like liposuction you can tell what it means. "oma" means tumor so the combination means fat tumor. Tumor simply means a swelling so it does not mean that it is cancer. Some tumors are cancerous and some are not. Most lipomas are non-cancerous but they can be unsightly or press on nerves. Then we operate.
Benign deep fat lump. Lipoma (lipo = fat, oma = tumor) is a benign (non-cancerous) skin-colored, protruding soft, compressible (squishy), solid, dome-shaped growth of fat under the skin and occurs independently of weight loss or gain. Multiple lipomas are usually inherited & very rarely cancerous (liposarcoma). Often confused with benign epidermal inclusion ("sebaceous") cysts or cheese-filled skin cavity.
It's a... ...Benign(ie, non-cancerous) tumor composed of slightly abnormal fat cells.