You can buy laptop bags in different designs. Especially popular are laptop sleeves, the so-called sleeves. These sleeves are the same size as your laptop and usually nothing else fits inside. Basically, these sleeves have only one function: to protect your laptop.
Of course, you can also buy laptop bags that can hold even more utensils. These are usually made of leather or textile. These include:
Laptop briefcase
Laptop case
Laptop shoulder bag
These laptop security options also provide ample space to store other documents or papers inside.

The dimensions of laptop bags correspond to the existing laptop sizes. For smaller laptops or tablets I advise you to use a laptop sleeve or tablet bag. As soon as your notebook exceeds a size of 13 or more inches, it makes sense to use a backpack, a briefcase, a suitcase or a shoulder bag for transport.
Basically, laptop bags have the following sizes:
13.3 in.
14 inch
15.6 inch
17.3 inch

Usually, laptop bags are made of nylon, polyester, leather or felt. For special requirements you can buy laptop bags made of imitation leather or neoprene.
There are also laptop cases or even trolleys that are made of aluminum. They absorb shocks better, but still convince with a certain lightness. However, they are also in a higher price segment.

This depends mainly on the material of your laptop bag. Felt or leather bags are definitely not waterproof. Nylon or polyester bags, on the other hand, are splash-proof.
If you are looking for a waterproof laptop bag, I recommend synthetic leather or neoprene. Alternatively, you can go for a laptop case. The only important thing is that the model has an IPX7 rating. This means that the bag can even withstand temporary submersion (maximum water depth of one meter / up to 30 minutes).

You should always pay attention to the material of the bag. Nylon, synthetic leather and neoprene bags can usually be put in the washing machine. All other materials should not be washed, as they are not designed for this purpose.
Leather, felt and polyester bags should not be washed. For these types of bags, I recommend using a damp cloth to remove dirt.