Ashwagandha is a root traditionally used for stress and calm. Shilajit is a mineral resin traditionally used for sustained energy and recovery. They are different materials with different traditional roles.
Many people take both. Both are food supplements and may help support general wellbeing as part of a balanced diet.
Ayor Health sells pure Himalayan shilajit resin in the UK from £34.99 (20g), £49.99 (30g) and £69.99 (50g). Every batch is independently tested by Eurofins UK and the reports are published in full at /lab-results.