`@while` is a loop inSASS that repeatedly executes a block of code as long as a given condition is true. For example:`$i: 1; @while $i <= 5 { .item-#{$i} { width: $i * 10px; } $i: $i + 1; }` generates classes `.item-1` through `.item-5`with increasing widths. This loop is useful for generating styles based on iterative conditions.