Google announced that at the end of June Google Tasks will become a core service of G Suite. It will be on by default for all domains.
Google Tasks is kind of like Google Keep without a bookmarking function. At its most basic level Google Tasks lets you create lists of tasks that you need to do and check them off as you complete them. Dig a little deeper into the app and you will find that you can create multiple lists for different projects or goals. Within each list you can create tasks and sub-tasks. Google Calendar is integrated into the app to let you set due dates for each task and task list.
Get the Google Tasks Android app here and get the Google Tasks iOS app here.