A Digital Certificate is like the identity of an individual, when he/she transacts/interacts through the internet it uniquely identifies any individual on the internet. It consists of an electronic file called "key pairs" containing the "Private key" and "Public key" of the individual to whom the Certificates belongs, which is digitally signed by the CA (Certifying Authority) to become a legally valid Digital Certificate / Digital Id.
A Digital Certificate can be used to electronically sign any document or transaction. It ensures that the data is secured and is not viewed or altered by any unauthorized person. It will also improve on response time taken while applying for a license with DGFT. It is also highly used with MCA - ROC Return and Income Tax Filing. Digital Certificates issued by a valid Indian CA hold good in a court of law in accordance to the Indian IT Act 2000
The Digital Signatures on any document remain valid throughout life,however the Digital Certificate being used to create the Digital Signature is valid for a period of one year and two years. After each year,therefore to keep using your digital certificate you need to pay just the renewed fees for your Certificates.
Using a Digital Certificate is one of the most secure ways of transacting over the Internet. Another important feature is that Certificate Enabled applications are accessed on secure socket layer SSL (E.g. https://dgft.gov.in/ instead of http://dgft.gov.in/). The SSL enables 128 bit encryption and data traveling between the clients (end user’s) browser to the web server of DGFT, MCA, Income Tax and for Railways thus making it impossible for anyone to steal information mid-way.
No you are not allowed to share your certificate with someone else. Giving any other person access to your Certificate is like allowing any other person to make use of your physical signature, Therefore it is illegal to allow it. The full responsibility of keeping the certificate safely lies with the certificate holders under Indian IT Act section.