Both is most commonly used with the conjunction "and". Both is used when 2 people or objects have the same characteristics or doing the same action. Both can come first in a sentence followed by the two subjects separated by and. Also both can be used in the middle sentence with indication that they are two subjects  without "and". Finally, the two subjects can come first in the sentence separated by "and" followed by "both".

Example:  Both Jim and Sally have blue eyes. 

Example: The two birds both flew away. 

Example: Tom and Harry both have books.