Where do you find icons?

Could you elaborate on where one might locate icons within the realm of cryptocurrency and finance? Are these icons typically found on specific platforms or applications? Do they serve as visual representations of cryptocurrencies or financial institutions? Is there a standard source for these icons, or do they vary depending on the user's preferences or the specific context? Additionally, are there any guidelines or best practices for selecting and using icons in this field to ensure clarity and consistency? Your insights would be greatly appreciated as I seek to enhance my understanding of this area.