Dynamics
Dynamics is about the sound pressure of the music and can physically be measured in decibels. Popularly speaking, it is about whether we should play weak or strong, or somewhere in between, and whether you should play with the same pressure throughout an entire song, or whether you should change it along the way. Dynamic expressions gives the music intensity. To go from a quiet passage to a strong will be experienced as an intensifying tension. Therefore, the dynamics helps to give the music expression. In the rhythmic tradition, in contrast to some of the classical (especially in the romance period) is not customary to change significantly in the music's overall tension in the course of a song or arrangement. The basic level of dynamics does basically not change significantly from start to finish. In some slow beat songs and musicals however there may be large dynamic range.
The force in which you hit the keyboard, of course, is very important for the dynamics of the music. You will find that there can be a large difference between the capabilities of different instruments in this regard. The larger and more expensive instrument, the better it will probably be able to play dynamically. A particular problem in this area is about the keystroke of the digital piano. In an electric piano it is in fact not a key, but a - advanced admittedly - on/off switch. On newer and more expensive digital pianos velocity has been improved in the recent years, but there is still a large diffent between the digital and acustis piano in this regard.
Three parameters exist in relation to dynamic piano playing: Keystroke (how heavily you hit the keys), quantity (how many notes are played at the same time) and pitch. .