Can I buy eSIM?

Excuse me, I was wondering if I could get some clarification on a topic related to technology and telecommunications. Specifically, I'm interested in understanding whether or not it's possible to purchase an eSIM. Could you please elaborate on what an eSIM is and if there are any specific requirements or limitations I should be aware of before making such a purchase? Additionally, could you provide some guidance on where I might be able to find an eSIM for sale, and if there are any particular brands or providers that you would recommend? Thank you in advance for your help and expertise in this matter.