Songwriters often just tell you how the music should feel. They might say “Rock”, or “Latin”. There are any number of simple instructions that will help you read the music the way they want you to.
Within the music itself you typically find expressive markings. The most frequent are probably the LOUD and SOFT instructions. The abbreviations for these are “f” and “p”. Originally the first pianos were called the loudsoft instrument-the Pianoforte. Unlike the harpsichord, it could be played at different volumes according to how hard or soft the keys were struck. So, f is loud, ff is louder, fff is really loud. The same arrangement follows with pianissimo-p is quiet, pp is quieter and so on.
Reading music often requires you to understand the Repeat Signs being used. Songwriters and composers take advantage of these shortcut symbols to reduce the number of measures and pages needed.
The ending of a song has 2 lines, a normal bar line line, then a thicker line. The end.
Before that the bracket with the number 1 tells the reader to repeat from the beginning, or at an earlier repeat sign. Then ignore any measure under the 1st ending bracket the 1st ending and play the 2nd ending measure(s) that follows.
Da Capo. Go to the beginning and repeat.
The Coda sign. It signifies a special section of music. During a repeat you would jump from the instruction a coda to the section marked Coda.
D.S. Del Segno. Go to the Segno sign and repeat.
The Segno sign.
A measure with a Bar line and an Ending Sign.
The picture below is a Repeat Sign. A Double Bar Line, one thicker than the other with dots above and below the middle line of the Staff.
The Repeat Sign means go back to the beginning, or to another repeat sign earlier in the song.
The Repeat Sign you would see earlier, if there was one.