The cap/base of a bulb is the part that connects it to the socket in the fixture. E27 (Edison screw) and E24 (small Edison screw) caps/bases are among the most popular, although this depends on your location. GU10 is generally the most common cap/base for spotlights. Check which cap/base you need carefully as many other types are also available.
Beam Angle (degree)
Luminous Flux (Lumen)
Lumen (lm) is the term used to describe the total amount of visible light emitted by a light source. The higher the number of lumens, the brighter it is.