A survey is typically made up of multiple questions while a poll is a one-question survey.
Not all survey question types are available for a poll. Question types such as contact information or text responses are not allowed as polls but single choice questions, ratings, and numeric scales are allowed. Once a recipient answers the poll question, they will be shown the results of the poll. Recipients will not be shown the results of a survey.
Surveys can gather more detailed information and will save into the constituent's record. They can be used to collect feedback from constituents and be used as applications for volunteers and memberships. Surveys can be sent via email, a URL link, or used internally to create a custom form. They also allow survey participants to upload documents for your review, accept electronic signatures, and can even process a payment if needed.