Is printer paper a4 or letter?

Is printer paper a4 or letter? What exactly is A4 paper, and why does it have a different name than the "standard" paper size?

Printer Paper Buying Guide

How To Print US Letter Templates On A4 Paper – Nina With Freckles

100% Pulp Copymate A4 Paper Printer A4 Legal Letter Size Copier Paper - China Copy Paper, A4 Paper

Sizing guides for A4 and letter-sized paper, BDS posted on the topic

Paper Sizes and Formats, the Difference Between A4 and Letter

Odaro Thermal Printer Paper 8.5 X 11 Us Letter Size Paper - Temu

A4 vs US Letter Between Borders

Paper Sizes Explained

800 Thermal Transfer Printer, Glossy, White at the lowest price at Temu. Free shipping and returns on office & school supplies on sale at Temu.

200pcs A4 Printer Paper, Multipurpose Copy Paper For Laser Printer, Inkjet Printer, Itari Copy Paper For Printer, Compatible With Phomemo P831 HPRT MT

What's A4 Size Paper & When to Use It