The Terrestrial Phase 1 Habitat Survey of Wales is a programme of field recording undertaken, in various stages, in the 1980s and 1990s. View the 'full summary' at that link to understand exactly what was surveyed when and how.
The main tranche of digitised data includes upland and lowland survey polygons and miscellaneous point data. An important upland boundary dataset is available separately. And a more recent dataset adds Traditional Orchards, which are not a distinct Phase 1 category.
On the map the extent of 'upland' is shown by a solid black line. Point data is represented (below 1:10000 scale) by small black circles. You can click anywhere to 'get feature info' (Phase 1 details) for a particular location. No attempt has been made to replicate the authentic Phase 1 colouring scheme. But some habitat types are coloured in the style used elsewhere for UK BAP Priority Habitats. See the chart below.