CELTA stands for Certificate in English Language Teaching to Adults. The CELTA used to be called CTEFLA (Certificate in Teaching English as a Foreign Language to Adults). The TESL certificate is a certificate in teaching English as a second language.
In the UK, the distinction between teaching English as a second language and teaching English as a foreign language is the following: for native speakers of Chinese, French, etc, etc, English is a foreign language. In countries such as India, English is a second language. The needs of learners of English as a second language are different to the needs of learners of English as a foreign language. I think that in the USA, this distinction does not exist.
It is difficult to answer your question about getting a job with these certificates. It will depend very much on the country and the school’s policy. Some schools ask for certificates, some like their teachers to have a diploma in teaching (a qualification higher than the cert), some take teachers with no qualifications and provide them with training. Most employers will give equal weight to a certificate in TEFL and TESL. The most important aspect in choosing a course is that the training centre should have a good reputation. You could take a look at the TEFL course database on this website for information about various courses.
I hope you will find a suitable course.
The information provided in this forum is intended for guidance only. We can only provide general information as situations vary from country to country. It should also be noted that economic and political situations change. We advise you to contact embassies and consulates before making decisions involving a move to another country. Tefl.net cannot be held responsible for any decisions you make based on the information provided here. It is your responsibility to gather information about employers before accepting a job.