You can use the Shortcuts bar (at the bottom of the screen) and combination keystrokes known as keyboard shortcuts to quickly perform many common actions.
While typing, you can do the following:
Accept a suggested word by tapping it in the Shortcuts bar.
Accept a suggestion highlighted in the Shortcuts bar by entering a space or punctuation. (If you enter a comma, period, or other punctuation after entering a space to accept a suggestion, the space is deleted.)
Reject the suggestions by tapping your original word (shown with quotation marks in the Shortcuts bar).
To turn off the suggestions, go to Settings Save keystrokes with text replacements.