Yes, many television programmes are subtitled, but this dependant on the channel / broadcaster. Read more on the Freeview Support page.You can enable subtitles going to Settings -> Accessibility -> Subtitle
Select the subtitle setting by pressing arrows keys on your remote control and choose the Option and then Confirm
The selected item will appear on the Accessibility page
You can also enable subtitles by playing the programme and selecting the setting icon on the programme panel displayed at the bottom of the screen. Use the right key on the remote to select the language subtitle you want.