The main way that mulch suppresses weeds is by preventing sunlight from penetrating the top part of the soil. Sunlight triggers weed seeds to germinate, but if you keep them in the dark they don't get a chance to grow.
So almost anything can work as a mulch, from pebbles to shredded paper, as long as it's keeping sunlight out of the soil.
There can be benefits to using different mulches for different parts of your garden. To make your ornamental garden beds look their best you might want dark or red woodchips so that your flowers or greenery really pop. But on new plantings and vegetable gardens you might want to use lucerne mulch, which breaks down relatively quickly, providing extra nutrients to the soil.
If you live in an area where termites are a problem, you might want to use cypress mulch, which is said to discourage termites. You might also want to use pebbles or scoria as mulch up against your house, so there is no wood on the ground to attract termites.
In the past I've also used newspapers and cardboard under other mulches, but I've personally gone off that now because I've come to think of it as a barrier to water entering the soil, and to the soil breathing and functioning normally.
One thing to keep in mind is that pebbles and stones can get very hot in the sun and bake the roots of shallow-rooted plants. Another is that if you use lawn clippings as mulch you'll probably be dumping loads of grass and weed seeds and cuttings into your garden beds. I'm never doing that again!
In the end you might find it's not a case of one size fits all. It might be about looking at the different needs of the different parts of your garden and maybe using a couple of different mulches. Spread it thick to keep the light out of the soil, but don't pile it around the trunks of trees and stems of plants because it can retain moisture and cause them to rot. - BradN
Another thing to remember is that over the years, mulch breaks down to the point where weeds can grow in the decomposed material. The most efficient way of removing weeds and eliminating further growth when it appears would be with a weed killer. Alternatively, you might like to place several layers of newspaper over the area and then re-mulch. You'll likely get a couple of years before this same process happens again. - MitchellMc
I have found (as I like to keep natural, no poisons to my gardener's dismay) that after first removing the weeds, put down white vinegar where you have removed them. Do this for 3 days, then once a week for maybe a month, or until you think the weeds are not coming back. Tea leaves after the vinegar is a good fertiliser. - Margie611
Mulch is certainly one of a gardener’s most valuable tools. It blocks weeds from resprouting, keeps roots cool in the heat of summer and provides a clean, organised aesthetic that makes it easier to navigate around your plants.
The Bunnings team has a helpful guide about mulch and how to use it, which includes a video. You can also learn how to install weed matting using the step-by-step guide. - Jason