What correct tile grout should be used

There are several types of grout on the market, and most are produced with different aspects in mind , grouting can be rigid or flexible ; which u would use if tiles are laid upon a wooden subrate( flexible grout will prevent the grout from cracking and breaking up) you can get grout especially for wet areas as most grouts are not totally waterproof . Personally I always if possible use a grout suitable for use on swimming pools, this product is slightly more expensive but will last much longer .

Around a shower unit requires a good quality grout, one of the best on the market is made by a company call 'BAL' they design grout especially for shower areas. Be aware that a top quality adhesive is just as important as the grout!