Timothy was a young leader, and this letter gives advice for young people about building good character and knowing truth. There is also some great advice on how to lead, both in general terms and specifically about dealing with difficult church situations.
This letter is a bit different from the others, as it was written to a person rather than a church. Timothy was a young leader who was put in charge of a church in Ephesus after Paul became concerned about its original leaders - so Timothy was mentored by Paul before going on to lead a church himself. This is a letter in which the wisdom of age is speaking to the passion of youth.