The basics
There are two extremes to traveling solo. One is to get away from your day to day life and just relax and not have a care in the world or be bothered by anyone. The other reason is to get out and meet people. Often times an itinerary falls somewhere in the middle.
If you want to just have a break from work to relax in the bliss of nature, a la Walden Pond or the Spa at the Four Seasons, traveling by yourself can give unparallel reflection. All the troubles of work and family slowly drift away. People are there to service your every need and your only prerogative is to enjoy.
Many are surprised how many more people they meet when they travel alone, not just other solo travelers, but groups are actually much more friendly and likely to approach a single traveler. Many say if you want to make friends travel solo, but if you want to lose friends travel with them. Not always the case of course, but many friendships are severely tested during long term travel together. Locals tend to approach you more as well. You really get involved with the local communities and cultures when you are alone.
A tangent of meeting people is finding love. Many travel for this purpose as well. Travelers tend to lose their inhibitions while on the road, so the chance of meeting someone tends to be high. Singles trips are popular for those looking for a little romance, although these are sometimes done with friends too.
Options for beginners
Beginning solo travelers tend to go not that far off the beaten path, and if they do they tend to go on a tour or with a group. Tour operators are friend of the solo traveler who doesn’t want to be completely alone. Traveling solo is much easier under the guidance of a tour group. You are still technically alone, but have the leadership and interaction of the guide and others in the group. You are alone, but will rarely feel alone. Everything from cruises, long distance hikes, and month long bus tours across Europe to bird and wildlife watching trips and research expeditions can be booked by the solo traveler.
Options for advanced
Solo travelers who have made a few trips on their own and want to get a little further from the main stream tours and destinations have plenty of options. These travelers put their vulnerability on the line, reach down into the pits of their stomach to find the will and courage to do something that may be difficult and frustrating. They face a risk of not meeting anyone, but are willing to take that chance. There are major rewards though. They can go anywhere they want. They aren’t stuck to the outline of a tour. When they need help they can hire everything they need from guides to horses. They go well off the beaten track. Places most tours don’t even go and can get deeply immersed in the local culture.