The “proportional set size” (PSS) the tool smem reports is the memory the program plus the “fair share” of each shared area to give a realistic measure. At simpletools.info the PSS is the crucial criterion to determine the memory footprint of a program. The unit is kilobyte (kB).
Most standard Unix memory tools are reporting the “resident set size” (RSS) - which roughly is the memory usage of a program plus the shared libraries it needs. Because it includes the whole shared memory it shares with other programs this isn't a fair representation of memory a program really needs.
The “unique set size” (USS) reports the memory needed by the program binary only, without any shared library it might need. This underestimates the programs memory footprint,unless it is a static linked binary.
Dynamic window managers can dynamically switch between tiling or floating window layout. It means you can change the arrangement of windows at any time.
There is a second definition in the context of tiling window managers: A dynamic tiling window manager is a window manager where windows are tiled based on preset layouts between which the user can switch.
When we talk about “dynamic window managers” we mean the former