Tallow shaving soaps are made mostly from beef fat, some soaps will have variants of other animal fats worked into the recipe, some additional or alternative options are sheep's fat, pig's fat (lard), donkey fat or ostrich oil. These soaps are mostly very slick and lathers well, they generally tick all the required boxes and have some of the best post shave qualities any soap can offer. Most soaps here are all natural, with some of them having only very basic ingredients to make it as soap that is suitable from the most sensitive skin and all skin types.
Tallow soaps in themselves can also vary quite a bit, some folks are also using other oils and butters in the mix, make sure your soap is a 'true tallow' by checking the ingredients and/or enquiring with the producer as to the percentages used.
Soaps vary from very hard to soft depending on the recipe and making process and can NOT be melted down to fit a container, tallow soaps must be grated if you want to change the form or container you received it in