VAT (used in the EU, UK, and most of the world) and GST (used in countries like Australia, Canada, and India) are functionally the same kind of tax under different names: a percentage added to the price of most goods and services, collected by the business selling them, and remitted to the government. Unlike US sales tax, VAT/GST is typically charged and reclaimed at every stage of a supply chain, with only the end consumer ultimately bearing the cost.
For a business, the practical complexity is usually around invoicing correctly — showing tax separately, applying the right rate for the right country and product category — and reclaiming VAT paid on business purchases against VAT collected on sales; the difference is what actually gets paid to the tax authority.
Rates vary enormously by country and even by product category within a country (many countries apply a reduced rate to food, books, or children's goods), which is why cross-border sellers usually need a tool that tracks current rates by jurisdiction rather than memorizing a single number.