Latex is used in manufacturing of two mattress parts: the "support part" and "upholstery layer".
Support part is made from "latex foam" and provides good support similar to spring mattresses, but latex is not a plastic foam, like polyurethane.
Latex is also used in protective fabric cover which encases the mattress. It is made to match the foundation and highly varies in colors and styles.

There are two distinctive types of latex - natural and synthetic. Natural latex is made from milky sap of plants that coagulate on exposure to air. Synthetic latex is made chemically.

Pros of latex mattresses:
Good durability.
Natural latex is hypoallergenic and antimicrobial material.
Breathable.

Cons:
Some people have a serious allergy to synthetic latex.
Natural latex is expensive due to natural sources of production material.

How to choose:
Choose one made from natural latex only.

Conclusion:
Latex mattress is an excellent choice if it suits your comfort feelings.