Call to Action’s (CTA’s) are exactly what they say on the tin, often a banner or text that tells the visitor to do something like buy a product or contact your business. Calls to action should be placed appropriately on the page as not to annoy visitors but to make it extremely easy for them to respond to. Every website should have an objective that it wants the visitor to complete. On ecommerce websites this is normally to buy a product but even for other types of websites these are important as you often want to engage users to register or contact you.
Often a very effective call to action is to show the user the problem they may have and offer a solution to that problem. This talks to people and if they connect with the issue and see that you can rectify it, they are very likely to click on your CTA.