Is Teaching English Overseas a real job?
Can I take it seriously?

If supporting yourself while living overseas and experiencing another culture is a goal, then yes you can consider TEFL a "real" job. 

If the possibility of saving substantially more money over a year than you could back home is your goal, then yes again.

If you would like to live overseas for extended periods and travel extensively, all while making a decent living, then yes, yes, yes, you can consider TEFL a "real" job.

Like any real job

Just like any "real" job back home, you can expect to start out at the bottom in EFL teaching. You will need to learn the ropes and should plan some study to improve your skills.  You will also need to network to improve your job possibilities and can expect periods of frustration and a difficult boss or coworker from time to time.  The "real" world doesn't go away overseas. 

You can expect that your employer will want you to make a serious effort at providing quality instruction for your students and will want you to represent the school/company/institution in a positive manner.  Employers will not see your job as a "lark" or a chance to see the world - they will want you to produce.  You will be expected to groom yourself, dress, and behave in a professional manner.  An out-of-the-ordinary personal appearance such as tattoos, piercings, oddly colored hair, etc. will make getting and keeping a job much more difficult.   

Unlike jobs back home

You might be hired without meeting your employer, might do just a telephone hiring interview, might have shorter work hours, fewer work days, longer vacations, free housing, airplane tickets to your new location, transportation to and from work and other "perks" that are not common back home.

Some things that are common in overseas hirings that you might not like include the need for a photograph accompanying your resume, interview questions about your marital status, family members and/or other non-work related issues.  Every country will be different in this regard - but you can certainly expect some surprises.