Bushwalking is the Australian word for hiking, or tramping. It is walking through undeveloped land or wilderness, on tracks, or cross-country through the bush. Australia is fortunate to have many large national parks which preserve scenic and rugged areas in their natural states. Even the largest city, Sydney, is (quite literally) surrounded by huge areas of national park.
The word "bushwalking" is derived from the title of the first hiking club in Sydney which was open to both genders. This club, formed in the late 1920's, was originally called the "Bush Walkers". Later the name of the club was changed to Sydney Bush Walkers (SBW). "Bush" is just an Australian term for our unique combination of Eucalypt forests, wildflowers and scrub.
Popular bushwalking locations within a few hours drive of Sydney include the Blue Mountains, Royal, Kanangra-Boyd, Wollemi, Budawangs and Morton national parks. Of these only the Blue Mountains and the Royal National Park are easily accessible by public transport.
Bushwalks may be just day-trips, or may last for several days or weeks. For overnight trips, a sleeping bag, light-weight tent (or fly), and cooking pots and/or fuel stove are also carried (see my printable checklist). Sometimes bushwalks are combined with other activities like canyoning or li-loing (floating along a river).
Good light-weight camping gear is not cheap. A backpack will cost around $300, a down sleeping bag between $100-$300, a Thermarest over $100, a stove $100-$200, a light hiking tent about $300, a good raincoat over $200. The total kit could easily cost over $1000! But you can gradually aquire all the gear as you do more trips, and once you've bought them, most items will last you for many years - if not a lifetime.