The problem solved by BFC?
1. Elements with BFC enabled will not be covered by floating elements
2. If BFC is not enabled, the parent-child outer margins will be merged
3. The element that opens BFC can contain sub elements (solve high collapse)
How to turn on BFC?
1. Float float is not a value of none
2. The value of position is not static or relative
3.display:inline-block table-cell table-caption flex inline-flex
4. Overflow is not visible
General use overflow:hidden
Each method of opening BFC has its own shortcomings. It can be selected according to the actual situation in the actual work, and avoid the insufficient points when meeting the needs.