SEO Audit is a process of checking hygiene and health factors of a website which includes the followings.
On Page Factors
Meta Descriptions Tags
Image Alt Tags
Content keywords relevancy
301 vs 302 Redirection
Off Page Factors
Search Engine Visibility
Types of SEO Audit
Basic Health SEO Audit: to make sure your website comply with all the basic SEO hygiene factors, you should for the basic seo health check. You must for this type of audit once at the time of new development or website redesign.
Competitive SEO Audit: If you want to complete with your competitors and drive higher visibility on the same keywords that your competitors are ranking on, then you must for the competitor’s analysis which generally includes the number of pages indexed by the search engine, back links, domain authority, keywords and content.
Traffic & Conversion rate SEO Audit: If you notice that your website is appearing in search engine rankings but you are not able to drive the traffic. If you are driving the traffic but its not converting then this type of SEO audit is must for you.
Penalty and Recovery audit: Panda and penguin are the two names which are quite popular but yes there are many more seo penalties which can affect your search engine ranking negatively and lead to huge traffic and visibility drop.
Negative SEO Audit: Negative SEO can be done by your competitors to rank you down in search engine pages. Do a periodic audit to make sure you are not attacked by the Negative SEO.