There are different sizes of the bulbs used in different parts of the world. more comprehensive guide at https://www.bulbs.com/learning/shapesandsizes.aspx, Most common are the

Bayonet types, having two pins to hang on to the holder, these are available in 2 sizes

• BC / B22 – Bayonet -22mm Diameter Base
• SBC / B15 – Small Bayonet – 15mm Diameter Base

Edison Types, having screw bases

• E-5 – Midget Screw
• E-10 – Miniature Screw
• E-11 – Mini Candelbra
• E-12 / C7 – Candelbra
• E-14 / SES (Small Edison Screw) – Eurpoean
• E-17 / C9 – Intermediate
• E-26 – Medium Base – mostly for US, 110V -140 V
• E-27 / ES (Edison Screw cap) – mostly ued in UK and Asia, 220V – 240V
• E-40 – Mogul Screw

Bi Pin Bases – more deatils can be found at https://www.12vmonster.com/blogs/product-questions/the-most-common-2-pin-fittings-and-their-uses

• G4
• GU4
• GU5.3
• GY6.35
• GU8
• GY8
• GY8.6
• G9
• G12