Depending on who you ask, the answer will change so this is actually a good question due to the fact it is subjective in its nature. An SEO Audit is an objective examination and assessment of your website and inspects the overall SEO effectiveness and identify where improvements can be made. Some SEO agencies may deem an SEO Audit to be limited to assessing technical SEO elements, improvements and best practices. For example, it would possibly identify issues with meta title and descriptions, keyword usage, alt/title tags. However, it may not investigate opportunities such as content marketing optimisation, social media optimisation and competitive marketplace insights.
By assessing the following areas and issues, you can begin to make improvements to improve your overall organic search performance and rankings:
Achieving Page One rankings is always the concern and goal but if you make the user journey and experience the main focus you will naturally start making SEO improvements. For example, users like a quick loading site that doesn't take ages to go between pages and it's not surprising that Google's likes site that load quickly.
A website SEO audit is essentially a “health check” for your website and the longer that a website is neglected it's not surprising the chance of more issues accumulating increases. Dependent on the website size, how many people maintain and update your website it will impact on your decision how often to review and audit your website (monthly, quarterly, yearly etc). Google is constantly improving and updating and you always hear about the next Google Algorithm looming but with regular monitoring and adhering to best practices you really shouldn't have to worry about these updates. Any good SEO Consultant will be looking at way within the SEO Audit and Review to be making recommendations that will future proof your website SEO Strategy.