The use of grace notes is an important expressive technique in all styles of piano playing. Grace notes have no real time of their own. Rather, they are heard as an expression added to the note they are leading to. A grace note is indicated by a very small note with a stroke through its stem. This note is played immediately before the following note, which is held for its full value.
There are two basic ways of playing grace notes. In Blues it is very common to play a grace note on a black key and then slide off onto a white key with the same finger. This technique is not used in classical piano playing, but is important in Blues playing.
The second technique does come from classical piano music. It involves playing a grace note on a white note and following it with either a black note or another white note. Each note is played with a different finger.
Here are some of the ways grace notes are commonly used in Blues and Boogie.
Here is a 12 Bar Blues solo which makes use of grace notes. The eighth notes in this example are played straight (i.e., not swung) Notice the new left hand pattern here. This pattern is common in Rock and Boogie piano playing.