The purpose of a telephonic interview can be many - checking communication skill to basic knowledge to ability to be driving the communication to being confident.
The reasons would best be known to the caller.
However to answer your queries -
This is a very basic question which is asked by an interviewer in order to allow you to speak. You should carefully chose the information to share at this stage as the answer to this question will decide the direction of the interview.
Many people when asked this question, take us through their CV which is something not expected as we have already gone through your CV. We need to know if there is anything that you wish to share not listed on CV. However if you have fed your CV with too much information, and have nothing much to speak except for revising your CV, I think it's high time to modify your CV.
Many people suggest that people start with their names which is much evident from the CV and that you should be focusing more on your achievements, the difficulties you faced during some of your projects and how you overcame it. etc.
Your current profile - I have seen many resumes that do state their current place of employment, their designation but they do not mention the joining dates.
They do mention their designation but do not list down a couple of points that will elaborate on what they did at their work place.
Ideally by this question we would like you to focus on how you are working on your current job, what challenges are you facing and how are you overcoming that.
The question is asked because though the designations are very clear, the job descriptions are not.
For eg: HR Executive can be a person in generalist role or recruitment role or on payroll. So unless specified the job role, how do we deduce the person's experience.
Again by this question, interviewer gives you a chance to prove your worth.
Do not take it negatively. Do not think that interviewer asked you this because he mentally rejected you and now wants you to sell yourself.
No.... That's not right.
We have not rejected you but we need to know how much do you understand the role, how do you fit into the role.
You should do a complete study on JD provided, highlight the skills required by them and mention any positive traits you have on those skills.
That is how ideally an interviewer would expect you to answer this and they do not want you to sell yourself but to be genuinely helping us to correlate our requirements and your skill set.
Who else can answer this but you? We need to know your strengths and weaknesses in order to understand how would you fit into the required role.
For Eg: You are being interviewed for sales executive's role and your weakness is lack of patience. I would know that you would not be able to handle severe situations when you need to handle clients very patiently.
This don't mean you should hide your weakness.
Accept your weak point (which will hamper your professional growth) and also let us know what are you doing to overcome that.
I hope I already answered your this question at the beginning of the post.
Hope it helped. All the best. :-)