A walk in shower includes a shower tray and shower screen as essentials, whilst the likes of sliding shower doors can feature in some versions. The general idea is you can step into the shower enclosure without having to open any doors, though.
Low level shower trays are a common fixture in walk in showers. However, the size of the shower tray you require will be dependent on the size of the bathroom or wet room, as well as the location of the floor joists and waste plumbing.
For a more detailed insight into walk in shower enclosures, take a look at our dedicated blog, 12 Wonderful Walk In Shower Ideas To Transform A Small Bathroom.