There are many different ways in which a note can be played, e.g. loud, soft, staccato, legato, etc. These different ways of playing a note are referred to as articulations. The way you articulate notes can make a dramatic difference to the way the music sounds.
In written music specific markings indicate the articulation desired by the composer. Two examples of this are shown below. For example, a short horizontal line directly above or below a note indicates that the note is to be held for its full written duration. This articulation is called tenuto. Another common articulation which you may already know is staccato, which means the note is to be played short and separate from other notes. Staccato is indicated by a dot placed directly above or below a note.
The following example contains both tenuto and staccato markings. Listen to the CD to hear the effect produced by each one. Experiment with these articulations in your playing by applying them to phrases you already know well and then try improvising with them. It is also important to listen to albums featuring your favorite players. Pay careful attention to how they articulate notes in different styles and situations. If you do this for even a few minutes each day# it will not take long before you begin to instinctively know how to articulate notes yourself.