mission pottery

It appears to have a couple of meanings. Firstly there are the handmade items that are made &/or sold through Christian or other missions. It tends to be handmade by the community. A couple of examples would be Amish and Shaker items; made by Amish/Shaker families and sold to raise funds for their communities, rather than for the individual or for a company.
It can also mean Mission Arts and Crafts, and Mission Revival, which was a turn of the century (1890-1915) style of architecture, decor and pottery, etc, that was influenced by the earlier Spanish Christian missions, such as the Franciscan Alta California missions (established 1769—1823). And companies such as Roseville, McCoy, Zanesville Stoneware Co, etc, produced items that are referred to as Arts & Crafts mission pottery.