牀 is the older, fuller form of 床 (bed). It writes the bed-board radical 爿 explicitly beside 木 (wood); the modern form 床 replaced 爿 with a roof 广. You meet 牀 only in classical and traditional texts.
爿 is a half-split log standing on end - the original picture of a bedstead. It supplies the core meaning of 牀, a frame to sleep on, and was dropped when the form simplified to 床.
No stroke data for 牀; the glyph shown is your device font, so component strokes can't be highlighted.
