A software bug is basically an error or flaw in a program that causes it to behave unexpectedly or crash. Bugs can be minor annoyances or major issues affecting functionality. I remember dealing with a tricky bug that interfered with payment processing when integrating magento 2 paypal express checkout. It caused orders to fail randomly, which was frustrating until the bug was identified and fixed. Bugs like this highlight why thorough testing is so important before release.