A standing wave or a stationary wave, is a wave that has parts that remain in a constant position

Nodes are points of no displacement - they remain in the same position. Particles at those points are not vibrating at all.

Antinodes are points on the waveform where the particles suffer maximum displacement.

Standing waves can occur when the medium is moving in the opposite direction to the wave, or it can arise in a stationary medium as a result of interference between two waves travelling in opposite directions (the usual source for a question at A level).

In the second case, for waves of equal amplitude travelling in opposing directions, there is on average no net propagation of energy. The energy 'stands still' so it is a standing wave - or is stationary - another way of putting it! The best way to get two waves of equal frequency, wavelength and amplitude so that you get completely destructive interference at the nodes is to reflect a wave from a fixed point.

See vibrations in a string