Understanding CSS Positioning

CSS positioning schemes control layout flow. There are five values: static, relative, absolute, fixed, and sticky. Each value alters an element's behavior in the document flow and its relationship to parents and siblings.

By default, elements use static positioning. They render in order, as they appear in the document flow. Static does not react to 'top', 'right', 'bottom', 'left', or 'z-index' properties.

Relative positioning allows element shifting from its normal position. Adjustments made with 'top', 'right', 'bottom', 'left' don't alter other elements' positions, causing possible overlap.

Absolutely positioned elements are removed from the flow and positioned relative to their nearest positioned ancestor. They can overlap other content and are placed using 'top', 'right', 'bottom', 'left'.

Fixed positioning anchors elements to the browser window. They remain in place during scrolling. This is useful for creating navbars or persistent UI elements. They ignore scrolling and resize events.

Sticky elements toggle between relative and fixed positioning based on scroll position. They 'stick' upon reaching a specified offset, typically used for headers or important calls to action.

Z-index works with positioned elements (relative, absolute, fixed, sticky) to control their stacking order. Without position, z-index has no effect. It's like layering stickers; higher values are on top.