Brading is much more than just your logo, it also includes the business colourways, fonts, uniforms and even company ethos! All of this together helps t build up a recognisable brand. If you think of companies such as McDonalds for example, you think of red and yellow, their mascot, their logo and also their uniform. All of their restaurants are easily recognisable and have some consistence no matter where they are. You can spot a McDonalds even in a different country.
Your branding and logo etc should be consistent throughout all your marketing whether it be online or offline. Some companies have branding for their premises but then when they get a website created, decide that they want to use something else. This can cause confusion for customers who may question whether you are in the same business. If they go on to your website and see the same branding as on the front of your shop they will then already have a certain amount of trust which is a very important part of selling online.
If you want to change your branding be sure to update everything as quickly as possible. You ideally want all your branding to match within a few weeks of introducing it.