Time is a very scarce resource and it does not get replaced as we go on wasting it. So, as with any other resource, you may want to know how you are spending it and why do you never have enough time. That is where time tracking software comes into play. It allows you to boost your productivity to a whole next level, as the best way to optimize something is to measure at and get feedback. For people who practice Pomodoro or Flowtime techniques time-tracking will streamline the process and get invaluable insights.
It can also help if you are a freelance or contractor worker, as you can define billable tasks and track how many hours you spent on them so you can adequately bill your customers. Or, if you are responsible for a programming team at work and you want to know how much in labor you are spending on each of the projects, time tracking can be of great help.
Most time tracking apps work pretty much the same: you define a set of Projects or Tasks and start the corresponding timer when you are working on one of them. The hardest thing about time tracking is to get into the habit of starting and stopping the timer when you begin working on something. It would at least take a couple of days to get used to, so do not worry if it does not work out at the very beginning. Consistency is key.
Time tracking can also help with procrastination, which I wrote about in my previous post.
Here are some of the tools (not ads or partnerships) that I have tried out and my thoughts on them:
Wakatime

Wakatime is a time-tracking tool specifically designed for programmers: it integrates into your IDE of choice and tracks how much time you spent writing code, which projects were you writing to, languages, etc. While it is certainly the easiest one, it will not allow you to track anything else but coding (for example, you may want to track time spent on writing the documentation, meetings, reading, etc).
Pricing: free (for personal use, up to 3 friends for leaderboard), $9/mon for premium.
Toggl

Toggl is a web-based, general-purpose time tracking solution. It is very rich in features and will suit any type of workflow. It also has apps for IOS and Android.
Pricing: free (for teams up to 5 people), $20 per user/month for premium.
Boosted

Boosted is only available as an app for IOS/Android, and it the simplest and easiest to use of them all. It has no paid features nor ads, comes with a concise UI and a dark theme. This is the one I use and my recommendation to go with it you are new to time tracking.