XML (Extensible Markup Language) is a text format that stores data inside named tags, so a file can carry both the value and a label for what that value means. A piece of data like <price>49.95</price> tells you the number is a price without anyone having to guess.
Think of it like a parcel with a packing slip on every item. Each thing inside is wrapped and labelled, so whoever opens the box knows exactly what is what. That self-describing nature is why XML stuck around for invoices, government data feeds and document formats: the structure travels with the data. Tags can nest too, so an order can hold a customer, who holds an address, who holds a postcode, all in one tidy tree. Its main trade-off is weight. XML repeats tag names a lot, which makes files larger and a bit slower to read than JSON. For a small record that hardly matters. For millions of rows it adds up fast.
You rarely read a whole XML file by hand. Instead you point a tool at the exact piece you want using XPath, a query syntax for walking the tag tree. And because the format is strict, a schema such as XSD can check that every required field is present and correctly typed, which is one form of data validation before the data ever reaches your system. A malformed invoice gets rejected at the door instead of corrupting a database three steps later.
At TopDevs we work with XML whenever a client integrates with banks, tax authorities or older partner systems that still speak it, and we convert it cleanly to whatever format the rest of their stack prefers.
