A mandala is a visual symbol often utilized in meditation practices and teachings. The mandala symbol itself is a geometric construction of points, lines, planes and solids symbolizing the universe. Mandalas are geometric designs depictive of the universe specifically. Other designs are similarly meditation tools, but may not be mandalas specifically. The visually conceived geometric symbols are visual meditation tools. A visual meditation tool is called a yantra. Mandalas and all other yantras are visual meditation points of concentration. Yantras are visual meditative tools similar in value to points of concentration. The image above is the sri yantra, sri meaning king or most important.
A mantra is the audio version of a mandala. A mantra is an audio meditation tool. Whether the sound of the mantra is a single syllable tone or a series of lengthy metaphysical musings, a mantra is an audio meditation tool. Mantras, as sound vibration, are wavy linear vibrations of connection.
The terms asana and mudra both reference physical positioning. An asana is a body posture as a meditation tool, and a mudra is a hand gesture or posture as a meditation tool. Asanas and mudras enable our own bodies to become a geometric representation of a meditation tool. The postures are physical meditation tools transforming self into one's own geometric figure or plane among the space and sensitive to the space of self and surroundings.
Tantra means unification, or looming/weaving together principles and practices, instruction and individual action. Tantra unites entirety. Tantra signifies confluence and integration; a fusion. It is Sanskrit for loom, the device which weaves together string into cloth. It is an ancient word with many properties and has been variously used to describe the knots of strings weaved together in a rug, and the cord on which sacred mala bead necklaces were strung, (Mala beads are Tibetan prayer necklaces of 108 beads used to assist mentally or vocally repeating a mantra 108 times.) and practices of unification of individual with the universal. Today the word tantra is often used in reference to the union of lovemaking. Though there is also a specific type of yoga called Tantra Yoga it means unification.
There is the potentiation of the unification of principle and practice. There is the potentiation of tantra of yantra, mantra and asana. And there is certainly the lesson of the potentiation of Yin Yang tantra. The combination of Yin and Yang potentials and energies within leads to all sorts of aspects of development. This can be energetically understood in the idea that there are only two types of energies, straight and circular, straight for Yang potentials and circular for Yin potentials. It can be understood on a tangible level that rest and work are both required. When straight and circular energies combine, a spiral results. A spiral is one of, if not the highest expressions of energy.
More broadly and generally, tantra notes a mutually accepted connection, a tied knot of intertwined being, like lovemaking, but not necessarily beginning with or limited to the act of lovemaking. Humanity itself is a tantra; a fused weaving knot or many strings, of many instructions and many individuals.
Essentially tantra is spiritual understanding of the relationship and connections between individuation and universal energies. An ancient spiritual philosophy preceding both Buddhism and Hinduism, tantra represents integration, unifying the macrocosm with the microcosm, the universal and the individual, the feminine and the masculine, the Yin and the Yang. It also refers to integrative knowledge and its continuation and building refinement through the interaction of teacher and student, signifying union and fusion; the acceptance, integration and transmutation of knowledge between individuals, like the string of life.