Broadly speaking, a "marketing strategy" can be defined as follows:
A business’ plan for getting in front of potential users and turning them into purchasers.
Depending on if your business is more transactional or relationship-focused, a marketing strategy can also own all the ways to encourage repeat website visits and purchases. Your strategy and goals are executed through a marketing plan, which breaks down the day-to-day structure for putting your ideas into action.
To get started crafting a yearly marketing strategy, establish a strong foundation by looking closely at how you're benchmarking against the previous years; (remember to add an asterisk for 2020 & 2021! It's likely your marketing strategy shifted dramatically given the extraordinary circumstances of living through a global pandemic).
This will help you establish the specific marketing goals and KPIs you want to achieve in 2023.