The tie "glues" two notes together to make a single longer note.
The tie is a curved line connecting the two notes. It looks like this:
You would play the above example as a single note that lasts for 2½
beats (2 beats for the half-note, plus ½ beat for the eighth-note).
Note: When you play and count tied notes, you do not need to
"do the math" and add up the note values; it's easier if you don't. You
can count the beats for each of the tied notes, one after the other, just like
you would if they were not tied. But when you get to the 2nd note (the
"tied-to" note), you don't start a new note; you just keep holding the
note you're already holding.
A dotted note lasts 1½ times as long as an "undotted"
note. We use dotted notes to write several common "odd" note lengths. A dotted
note is a "plain note" with a dot after it. Here are the common dotted