The vast majority of the content on the internet has some sort of copyright, but typically it is very hard to police if someone has taken all or a portion of your work. There are ways to officially apply for a copyright using some of the online legal document services available on this site and others. However, most people are content to put a copyright notice at the bottom of their creation and just hope that it does not get stolen or reproduced without their permission. For more extensive works such as books or large publications it would be prudent to apply for an official copyright using an online legal document service.
A trademark is available for businesses and others who want to afford some sort of extra protection to their ideas and brand name. Obviously, if some other company sprouted up and started sporting the tag-line "Just Do It(TM)", Nike would not be happy. They have invested millions and millions of dollars into creating the brand image that is associated with the tagline. Although most businesses and individuals do not need the protection that Nike can afford, there are inexpensive alternatives.
Trademarks can be acquired online through an application process that typically will total you less than $500. For more advanced users who want to have active protection on their ideas or brand, there are also services that will monitor your trademark. The trademark monitoring service basically is a periodic scan of the trademark database for possible conflicts. If someone files a trademark that could be a possible infringement on your own trademark, you would be notified. This is the point at which the client would need to move on to an actual lawyer, because the legal document service can only do so much. If the trademark infringement is determined to be valid, further legal action would be required.
Trademarks and copyrights are very important to businesses and publishers, especially when your original work or content constitutes your livelihood. Spend careful time considering how much money it is worth to protect yourself from possible thieves or plagiarism. If the business DIRECTLY relates to the original content or brand image, it would be advisable to officially apply for protection of your ideas.