A magnet is by definition an object with magnetic properties (magnetism) that attracts iron and produces a magnetic field. It can be a permanent magnet or an electromagnet.
Permanent magnets do not rely upon outside influences to generate their field. In permanent magnets are the atoms and molecules ordered in long range. The specific electron configuration and the distance of the atoms is what lead to this long range ordering. The electrons exist in a lower energy state if they all have the same orientation. Magnetic domains can be likened to microscopic neighborhoods in which there is a strong reinforcing interaction between particles, resulting in a high degree of order. The greater the degree of ordering within and between domains, the greater the resulting field will be. Long range ordering is one of the hallmarks of a ferromagnetic material.
A current carrying conductor for example a piece of wire, produces a magnetic field that encircles the wire. An electromagnet, in its simplest form, is a wire that has been coiled into one or more loops. This coil is known as a solenoid. The more loops of wire and the greater the current, the stronger the field will be.
Superconducting magnets are a special type of electromagnets, often used in MRI machines with high field strength.

Temporal stability of the magnetic field. Factors to be considered are field decay of superconducting magnets in persistent mode, aging of permanent magnet material, temperature dependence of permanent magnet material, and temporal stability of magnet power supplies.

North and south magnetic poles separated by a finite distance. An electric current loop, including the effective current of a spinning nucleon or nucleus, can create an equivalent magnetic dipole.

(H) The region surrounding a magnet (or current carrying conductor) is equipped with certain properties like that a small magnet in such a region experiences a torque that tends to align it in a given direction. Magnetic field is a vector quantity; the direction of the field is defined as the direction that the north pole of the small magnet points when in equilibrium.

A magnetic field produces a magnetizing force on a body within it. Although the dangers of large magnetic fields are largely hypothetical, this is an area of potential concern for safety limits. Formally, the forces experienced by moving charged particles, current carrying wires, and small magnets in the vicinity of magnet are due to magnetic induction (B), which includes the effect of magnetization, while the magnetic field (H) is defined so as not to include magnetization. However, both B and H are often loosely used to denote magnetic fields.

Magnetic field gradients are used to change the strength of the magnetic field Bo in a certain direction. Gradients are used in MR imaging with selective excitation to select a region for imaging and also to be able to encode the location of MR signals received from the object being imaged. The field strength is measured in Tesla per meter (T/m).